Pesticides



EESTICIDES Abraham Bavley, Brooklyn, and Donald P. Cameron, Bronx, N. Y., assignors to Chas. Pfizer & Co., Inc., Brooklyn, N. Y., a corporation of Delaware N Drawing. Application July 2, 1957 Serial No. 669,452

6 Claims. (Cl. 167-30) This invention is concerned with a new class of pesticides valuable in combating insects and particularly usescribed more fully hereinafter.

The wide-spread and eifective use of insecticides has given rise to a new problem, that is the control of mites. The removal of insects, particularly of insects which are the natural enemies of mites, has progressed to the point where various species of mites formerly considered serious pests only occasionally, or in restricted areas, have caused grave injury each season to many economically important crops. The compounds of this invention are unusually efiective in the control of mites. These compounds are dialkylthiono-phosphonothio substituted derivatives of ethyl and propyl fully esterified substituted and unsubstituted mono-nuclear aromatic dicarboxylic acid esters, the alkyl groups on said dialkylthionophospho-nothio substituents containing up to four carbon atoms, and the substituents on an aromatic nucleus being alkyl or alkoxy containing up to four carbon atoms. The acids whose derivatives are included within the purview of this invention are phthalic, iso-phthalic, terephthalic and alkyl and alkoxy derivatives of phthalic, isophthalic and terephthalic acid, the alkyl and alkoxy groups containing up to four carbon atoms.

Thus the compounds of this invention can be illustrated by the following formula:

or a propyl ester. For an ethyl ester, the most desirable starting compound is a fully esterified ,B-haloethyl ester of the selected dicarboxylic acid, preferably a fi-chloroethyl ester. For a propyl ester derivative, the most desirable starting compound is a fully esterified allyl ester. When the terms, fi-haloethyl ester, allyl ester, ethyl ester or propyl ester are used hereinafter, it is to be understood that reference is made to a fully esterified dicarboxylic acid, that is one with no free carboxyl groups.

ethyl esters of the instant invention.

2,865,804 Patented Dec. 23, 1958 ice The above starting compounds as used in the preparation of the products of this invention can be readily prepared by a number of procedures as will be apparent to those skilled in the art. It has been found that theirhaloethyl esters are very readily prepared by the reaction of a halohydrin, for example, chlorohydrin with the chosen acid using conventional Fischer esterification procedures. Fischer esterification procedures can be similarly employed for the preparation of allyl esters by the reaction of allyl alcohol with the chosen acid.

A metathetical reaction between an ammonium or metallic salt of,dialkyldithiophosphoric acid, preferably the ammonium or alkali metal salt, and a fl-haloethyl ester provides the valuable dialkylthionophosphonothio- This reaction is conveniently carried out by contacting the chosen fi-haloethyl ester with the chosen salt in a lower, aliphatic, oxygenated solvent such as the lower alkanols and ketones containing up to six carbon atoms at a temperature of from about Cato about 150 C. for a period of from about fifteen minutes to about six hours.

It may be advantageous to use as much as fifty percent excess or even more of the dialkyldithiophosphoric acid to insure high yields, but it is not necessary to do so, since an equivalent quantity of the acid provides quite good yields. which, at atmospheric conditions, boils within the preferred temperature range of fro-m about C. to about C. and to reflux the mixture for the preferred reaction period of from about thirty minutes to about two hours. During the reaction period the by-product, inorganic salt, for example, sodium chloride usually precipitates from the mixture and this can be removed gby filtration.

The valuable product can be recovered in any convenient manner, for example, solvent extraction or removal of the solvent in vacuo. The compounds of this invention are so active as pesticidal agents that it is not necessary to use them in a highly purified form, therefore, in most instances, the product will be recovered by simply removing the solvent in vacuo. It may be desirable to filter the residue before use to remove the last traces of inorganic salt.

If a highly purified product is desired this can be readily obtained. For example the less pure product can be taken up in a water immiscible solvent or a mixture ofsolvents, say for example, aliphatic or aromatic hydrocarbon solvents containing up to ten carbon atoms or a mixture of these with dialttyl ethers containing up to eight carbon atoms. The solution is then washed with water, dried and the solvent removed in vacuo. The residue from the washed solution can be further purified by conventional means, for example recrystallization or vacuum distillation.

A dialkyldithionophosphonothiopropyl ester of this invention can be prepared by reaction between an allyl ester and a dialkyldithiophosphoric acid. This reaction is carried out by contacting the chosen ester with at least an equivalent proportion of the chosen acid in an inert organic solvent, for example lower, aliphatic or aromatic hydrocarbon solvents containing up to ten carbon atoms, and their halogenated analogs, at a temperature of from about 60 C. to about 180 C., for from about six to about thirty-six hours. Suitable solvents include heptane, octane, benzene, toluene, the xylenes, chloroform, carbon tetrachloride, chlorobenzene, etc. It is most convenient to select a solvent which, under atmospheric conditions, boils within the preferred temperature range of from about 80 C. to about C., and to reflux the mixture for the preferred time of from about sixteen to about thirty hours.

It is most convenient to select a solvent The product can be recovered from the reaction mix- .ture by any convenient method. As with the ethyl analogs, the propyl compounds are so active that it is not necessary to employ the highly purified compounds,

"and hence the compound will most often be isolated by removing the solvent in vacuo. Itv is best to neutralize any excess acid by washing the reaction mixture with an aqueous alkaline reagent, for example, the hydroxides, carbonates or bicarbonates of the alkali or alkaline earth metals, prior to removing the solvent. The neutralizatron is usually preceded and followed by an aqueous wash. The reaction mixture is best dried before stripping the solvent in vacuo, and this can be accomplished by the use of an anhydrous drying agent, such as sodium ormagnesium sulfate. It may be convenient to choose a solvent which forms an azeotropic mixture with water,

:tnd to dry the reaction mixture byazeotropic distillaron.

" The highly purified product can be obtained by the same procedure used for preparing the purified ethyl i analog.

In carrying out the above described reaction it may be advantageous to use as much as a fifty percent excess, or even more, of the dialkyldithio-phosphoric cid to insure high yields, but it is not necessary to do so since an equivalent quantity of the acid provides quite good yields.

As stated above, the compounds of this invention are valuable in combating insects, particularly mites. For

the purpose of combating insects the compound may be used alone or dispersed in a suitable extending agent.

One particularly effective manner of applying the miticidal agents of this invention is to suspend the chosen compound in a 5% acetone-water solution and to apply the mixture in the form of a spray. Mixtures of this type containing as little as 60 parts per million of active pesticidal agent are effective in combating Telranychus bimapulata, commonly known as the two-spotted spider mite. This particular mite causes extensive damage to both hothouse and open air crops. It is a general feeder but particularly troublesome to cucumbers, tomatoes, roses, chrysanthemums, fuchsias and argenatums. It is a major problem on roses.

cularly in those areas which have been extensively treated with common insecticides. V

Mites present a peculiar control problem. Their life cycle is so short that there is nearly always a sufiiciently high proportion of the population in the egg stage to render miticides which are effective only against the nymph or adult stage of the mite unsatisfactory. Thus, a mitiycide which is lethal only towards nymph and adult mites does not give complete control, since the eggs which have not hatched, will hatch and the mite will mature after the the term, dispersed is used in its widest possible sense. When it is said that the compounds of this invention are dispersed it means that the particles may be molecular in size and held in true solution in a suitable solvent. It

means further, that the particle may be colloidal in size and dispersed through a liquid phase in the form of suspension or emulsions or in the form of particles held in suspension by wetting agents. It also includes particles which are dispersed in a semi-solid viscous carrier such as petrolatum or soap in which they may be actually dissolved in the carrier or held in suspension in the carrier When it is not controlled it limits production of edible crops and makes flowers unsalable. It has become increasingly prevalent in orchards, partiwith the aid of suitable emulsifying or wetting agents. The term, "dispersed also means that the particles may be mixed with and spread throughout a solid carrier so that the mixture is in the form of powder or dust. The term, dispersed also includes mixtures which are suitable for use as aerosols including solutions, suspensions or emulsions of the agents of this invention in a carrier such as Freon which boils below room temperature at ordinary pressure.

The term, extending agent as used in this disclosure, and in the appended claims, includes any and all of those agents in which the compounds of the instant invention are dispersed. It includes, therefore, the solvents of a true solution, the liquid phase of'suspensions, emulsions or aerosols, the semi-solid carrier of ointments and the solid phase of dust and powders.

It has been found that the compounds of this invention are active when dispersed in an extending agent at concentrations of 0.001 percent by weight or even lower. This concentration is effective when the dispersing agent is a liquid but it is preferred to use more concentrated mixtures when the dispersing agent is a semi-solid or a solid. This is because liquid dispersions which are, of course, suitable for. use as sprays give a more intimate contact with the mites than the solid dispersions and, therefore, lower concentrations are more effective with liquid dispersions. I

There area number of solvents which can be utilized for the preparation of solutions, suspensions or emulsions of the compounds of thm invention. High boiling oils of vegetable origin such as castor oil or olive oil have been found to be suitable. Low boiling, more volatile solvents such as acetone, cyclohexanone, carbon tetrachloride, ethylene dichloride, tetrachloroethane, hydrogenated naphthalenes, alkylated naphthalenes, solvent naphtha and the like are also useful. Petroleum fractions, particularly kerosene, are especially useful. For certain applications it may be advantageous to resort to mixtures of solvents.

If the active agents are to be applied as aerosols it is convenient to dissolve them in a suitable solvent and to disperse the resulting solution in a liquid such as Freon which boils below room temperature. For such applications it is better to employ true solutions of the active agent although it is possible to employ suspensions or emulsions of the active agent.

The agents of this invention are often dispersed either in the form of emulsions or suspensions, in an inert carrier such as water with the aid of a capillary active substance. Such capillary substances may be anion-active, cationactive or non-ionizing. There may be mentioned by way of example natural or synthetic soaps, Turkey-red oil, fatty alcohol sulfonates, esters of fatty acids and the like. Other examples include high molecular weight quaternary ammonium compounds as well as condensation products of ethylene and propylene oxide with monohydric and polyhydric alcohols.

For use as a powder or dust the active ingredients of this invention are mixed with any of a number of extending agents either organic or inorganic in nature which are suitable for the manufacture of pulverulent prepara tions. This includes, for example, tricalcium phosphate, calcium carbonate, kaolin, bole, kieselguhr, talcum, calcined magnesia, boric acid and others. Materials of vegetable origin such as powdered cork, powdered wood and powdered walnut shells are also useful. These mixtures may be used in the dry form, or by the addition of wetting agents, the dry powder can be rendered wettable by water so as to obtain stable aqueous dispersions suitable for use as sprays.

For special purposes the agents of this invention can be worked into the form of a paste or an ointment by the use of such semi-solid extending agents as soap or petroleum jelly with or without the aid of solubility prometers and/or dispersing agents In all of the forms described abovethe dispersions may be provided ready for use or they maybe provided in a concentrated form suitable for mixing with other extending agents before use.

In all of these various dispersions the active 'pesticidal a ents can be one of or a plurality of the compounds of our invention. The compounds may also be advantageously employed in combination with other pesicides including for example, insecticides, fungicides and bac tericides. There may be mentioned by way of example, 1,1-bis-(p-chlorophenyl) 2,2,2 trichloroethane (DDT); the gamma isomer of benzene hexachloride; 2,2-bis- (p-methoxy phenyl)-l,1,1-trichloroethane (DMDT); or inorganic compounds such as salts of mercury, copper or arsenic, as well as finely divided sulphur. In this manner it is possible to obtain mixtures which are effective against a wide variety of pests.

The following examples are given by way of illustration only and are not to be construed as limitations of this invention, many variations of which are possible without departing from the spirit or scope thereof.

7 EXAMPLE I di-3-(dimethylthionophosphonothi0) propyl isophthalate water, three times with 50 ml. of 10% sodium bicar- I bonate and again with a 50 ml. portion of water. The organic layer was separated and dried over anhydrous magnesium sulfate, filtered and concentrated at 5 mm. of mercury for twelve hours at room temperature to leave the desired product as a residue.

EXAMPLE II di-3-(diethylthionophosphonothi0) propyl-Z-propoxy isophthalate 2-propoxy-diallyl isophthalate (0.1 mole) in 100 ml. of toluene plus 0.2 mole of diethyldithiophosphoric acid was heated under reflux for twenty-four hours. It was cooled and concentrated in vacuo at room temperature. The residue was taken up in 150 ml. of toluene, washed once with 50 ml. of water, three times with 50 ml. of 10% sodium bicarbonate and again with a 50 ml. portion of water. The organic layer was separated and dried over anhydrous sodium sulfate, filtered and concentrated at 5 mm. of mercury for twelve hours at room temperature to leave the desired product as a residue.

EXAMPLE III di-3-(dipropylthionophosphonothio) pr0pyl-4-but0xy isophthalate 4-butoxy-diallyl isophthalate (0.1 mole) in 100 ml. of

chloroform plus 0.2 mole of dipropyldithiophosphoric EXAMPLE IV di-3-(dimethylthionophosphono) propyl-S-methoxy isophthalate S-methoxy-diallyl,isophthalate (0.1 mole) in 100-ml. of carbon tetrachloride plus 0.3 mole of dimethyldithiophosphoric acid was heated under-reflux for six hours. It was cooled and concentrated in vacuo at :room temperature.

6 The residue was taken up in 150 ml. of carbon tetra chloride, washed once with 50 ml. of water, three times with 50 ml. of 10% sodium bicarbonate and again with a 50 ml. portion of water. The organic layer wasseparated and dried .over anhydrous sodium sulfate, filtered and concentrated at 5 mm. of mercury for twelve hours at room temperature to leave the desired product as a residue.

EXAMPLE V di-3-(dimethylthionophosphonothio) propyl-S-methyl isophthalate S-methyl-diallyl isophthalate (0.1 mole) in ml. of heptane plus 0.2 mole of dimethyldithiophosphoric acid was heated under reflux for twenty hours. It was cooled and concentrated in vacuo at room temperature. The residue was taken up in ml. of heptane, washed once with 50 ml. of water, three times with 50 ml. of 10% sodium bicarbonate and again with a 50 ml. portion of water. The organic layer was separated and dried over anhydrous sodium sulfate, filtered and concentrated at 5 mm. of mercury for twelve hours at room temperature to leave the desired product as a residue.

EXAMPLE VI di-3-(dimethylthionophosphonothio) propyl phthalate Diallyl phthalate (0.1 mole) in 100 ml. of benzene plus 0.25 mole of dimethyldithiophosphoric acid was heated under reflux for twenty-four hours. It was cooled and concentrated in vacuo at room temperature. The residue was taken up in 150 ml. of benzene, washed once wi.h 50 ml. of water, three times with 50 ml. of 10% sodium bicarbonate and again with a 50 ml. portion of water. The organic layer was separated and dried over anhydrous magnesium sulfate, filtered and concentrated at 5 mm. of mercury for twelve hours at room temperature to leave the desired productas a residue.

EXAMPLE VII di-3-(diethylthionophosphonothi0) pr0pyl-3,4-dimeth0xy phthalate 3,4-dimethoxy-diallyl phthalate (0.1 mole) in 100 ml. of o-xylene plus 0.3 mole of diethyldithiophosphoric acid was heated under reflux for twenty hours Itwas cooled and concentrated in vacuo at room temperature. The residue was taken up in 150 ml. of o-xylene, washed once wi h 50 ml. of water, three times with 50 ml. of 10% sodium bicarbonate and again with a 50 ml. portion of water. The organic layer was separated and dried over anhydrous sodium sulfate, filtered and concentrated at 5 mm. of mercury for twelve hours at room temperature to leave the desired product as a residue.

EXAMPLE VIII di-3-(dibutylthionophosphonothio) propyl-3-ethoxy phthalate 3-ethoxy diallyl phthalate (0.1 mole) in 100 ml. of toluene plus 0.27 mole of dibutyldithiophosphoric acid was heated under reflux for twenty-four hours. It was cooled and concentrated in vacuo at room temperature. The residue was taken up in 150 ml. of toluene, washed once with 50 ml. of water, three times with 50 ml. of 10% sodium bicarbonate and again with a 50 ml. portion of water. The organic layer was separated and dried over anhydrous magnesium sulfate, filtered and concentrated at 5 mm. of mercury for twelve hours at room temperature to leave the desired product as a residue.

was heated under reflux for twenty hours. It was cooled and concentrated in vacuo .at room temperature. The

' residue wastaken up in 150 ml. of benzene, washed once with 50 ml. of water, three times with 50 ml. of 10% sodium bicarbonate and again with a 50 ml. portion of water. The organic layer was separated and dried over anhydrous sodium sulfate, filtered and concentrated at mm. of mercury for twelve hours at room temperature to leave the desired product as a residue.

, EXAMPLE X Di [3-(dimethylthionophosphonathio) propyll terphthalafe The organic layer was separated and dried over anhydrous magnesium sulfate, filtered and concentrated at 5 mm. of mercury for twelve hours at room temperature to leave the desired product as a residue.

EXAMPLE XI Di[3-(diethylthionophosphonothio) pr0pyl1-5-butyl isophthalate S-butyl-diallyl isophthalate (0.1 mole) in 100 ml. of benzene plus 0.3 mole of diethyldithiophosphoric acid was maintained at a temperature of 60 C. for thirty-six hours. It was cooled and concentrated in vacuo at room temperature. The residue was taken up in 150 ml. of benzene, washed once with 50 ml. of water, three times with 50 ml. of sodium bicarbonate and again with a 50 ml. portion of water. The organic layer was separated and dried over anhydrous toluene, filtered and concentrated at'5 mm. of mercury for twelve hours at room temperature to leave the desired product as a residue.

EXAMPLE XII Di [2-(dimethylthionophosphonothio) ethyl] isophthalate of'benzene containing 25 ml. of diethyl ether and the resulting solution washed twice with 25 ml. portions of water. The organic layer was separated. and dried over magnesium sulfate. The drying agent was removed by filtration and the dried filtrate concentrated at 0.5 mm. of mercury for twelve hours at room temperature to leave the desired product as a residue.

EXAMPLE XIII Di [2-(diethylthianophonothio) ethyl] -4,6-dimethyl isophthalate To a stirred solution of 0.1 mole of barium diethyldithiophosphate in 75 ml. of methanol was added, over 0.25 hour, 0.23 mole of di-(Z-bromoethyl) isophthalate while maintaining the solution at the reflux temperature. Refiuxing was continued for one hour and at the end of this period precipitated barium bromide was removed by filtration. The filtrate was concentrated in vacuo at room temperature. The residue was taken up in 100 ml. of benzene and the resulting solution washed twice with 25 ml. portions of water. The organic layer was separated and dried over sodium sulfate. The drying agent was removed by filtration and the dried filtrate concentrated at 0.5 mm. of mercury for twelve hours-at room temperature to leave the desired product as a residue.

8 EXAMPLE XIV DiEZ-(dimethylthionophosphonothio) etlzylJ-Z-propoxy isophthalate To a stirred solution of 0.1 mole of ammonium dimethyldithiophosphate in ml. of methyl ethyl ketone was added, over 0.25 hour, 0.3 mole of 2-propoxy-di-(2-chloroethyl) isophthalate while maintaining the solution at the reflux temperature. Refluxing was continued for 1.5 hours and at the end of this period precipitated ammonium chloride was removed by filtration. The filtrate was concentrated in vacuo at room temperature. The residue was taken up in 100 ml. of benzene and the resulting solution washed twice with 25 ml. portions of water. The organic layer was separated and dried over magnesium sulfate. The drying agent was removed by filtration and the dried filtrate concentrated at 0.5 mm. of mercury for twelve hours at room temperature to leave the desired product as a residue. 7

EXAMPLE XV Di[2-(Jimethylthionophosphono) ethyl1-4-mezhoxy isophthalate To a stirred solution of 0.1 mole of potassium dimethyldithioposphate in 100 ml. of methyl propyl ketone was added, over 0.5 hour, 0.45 mole of 4-methoxy-di-(2- chloroethyl) isophthalate while maintaining the solution at the reflux temperature. Refluxing was continued for 1.5 hours and at the end of this period precipitated potassium chloride was removed by filtration. The filtrate was concentrated in vacuo at room temperature. The residue was taken up in 100 ml. of toluene containing 25 ml. of dibutyl ether and the resulting solution washed twice with 25 ml. portions of water. The organic layer was separated and dried over sodium sulfate. The drying agent was removed by filtration and the dried filtrate concentrated at 0.5 mm. of mercury for twelve hours at room temperature to leave the desired product as a residue.

EXAMPLE XVI Di[2-(diethylthionophosphonothio) ethyl1-5-but0xy isophthalate To a stirred solution of 0.1 mole of ammonium diethylidithiophosphate in 100 ml. of hexanol was added, over 0.5 hour, 0.25 mole of 5butoxy-di-(Z-chloroethyl) isophthalate while maintaining the solution at the reflux temperature. Refluxing was continued for two hours and at the end of this period precipitated ammonium chloride was removed by filtration. The filtrate was concentrated in vacuo at room temperature. The residue was taken up in 100 ml. of benzene and the resulting solution washed twice with 25 ml. portions of water. The organic layer was separated and dried over magnesium sulfate. The drying agent was removed by filtration and the dried filtrate concentrated at 0.5 mm. of mercury for twelve hours at room temperature to leave the desired product as a residue.

EXAMPLE XVII Di [2-(dimelhylthionophosphonothi0) ethyl] -5-methyl isophthalate To a stirred solution of 0.1 mole of sodium dimethyldithiophosphate in 100 ml. of isopropanol was added, over 0.25 hour, 0.25 mole of S-methyl di(2-bromoethyl) isophthalate while maintaining the solution at the reflux temperature. Refiuxing was continued for five hours and at the end of this period precipitated sodium bromide was removed by filtration. The filtrate was concentrated in vacuo at room temperature. The residue was taken up in 100 ml. of heptane and the resulting solution washed twice with 25 ml. portions of water. The organic layer was separated and dried over sodium sulfate. The drying agent was removed by filtration and the dried filtrate concentrated at 0.5 mm. of mercury for twelve hours at room temperature to leave the desired product as a residue.

9 EXAMPLE XVIII Di [2-(dimethylthionophasphonothio) ethyl] phthalate The drying agent was removed by filtration and the dried temperature. Refiuxing was continued for three hours and at the end of this period precipitated ammonium chloride was removed by filtration. The filtrate was concentrated in vacuo at room temperature. The residue was taken up in 100 ml. of benzene and the resulting solution washed twice with 25 ml. portions of water. The organic layer was separated and dried over sodium sulfate.

' filtrate concentrated at 0.5 mm. of mercury for twelve 25 ml. portions of water. The organic layer was separated and dried over ammonium chloride. The drying agent was removed by filtration and the dried filtrate concentrated at 0.5 mm. of mercury for twelve hours at room temperature to leave the desired product as a residue.

EXAMPLE XIX Di[2-(diethylthionophosphonothi0) ethyl]-3,4-dipr0poxy phthalate To a stirred solution of 0.1 mole of ammonium diethyldithiophosphate in 100 m1. of ethanol was added, over 0.1 hour, 0.25 mole of 3,4-dipropoxy-di-(2-chloroethyl) phthalate while maintaining the solution at the reflux temperature. Refiuxing was continued for 0.5 hour and at the end of this period precipitated ammonium chloride was removed by filtration. The filtrate was concentrated in vacuo at room temperature. The residue was taken up in 100 ml. of benzene and the resulting solution washed twice with 25 ml. portions of water. The organic layer was separated and dried over sodium sulfate. The drying agent was removed by filtration and the dried filtrate concentrated at 0.5 mm. of mercury for twelve hours at room temperature to leave the desired product as a residue.

EXAMPLE XX Di [2-(dipropylthionophosphonothio) ethyll-3-ethoxy phthalate To a stirred solution of 0.1 mole of ammonium dipropyldithiophosphate in 100 ml. of methyl ethyl ketone was added, over 0.5 hour, 0.2 mole of 3-ethoxy-di-(2- bromoethyl) phthalate while maintaining the solution at the reflux temperature. Refluxing was continued for one hour and at the end of this period precipitated ammonium bromide was removed by filtration. The filtrate was concentrated in vacuo at room temperature. The residue was taken up in 100 ml. of benzene and the resulting solution washed twice with 25 ml. portions of water. The organic layer was separated and dried over sodium sulfate. The drying agent was removed by filtration and the dried filtrate concentrated at 0.5 mm. of mercury for twelve hours at room temperature to leave the desired product as a residue.

EXAMPLE XXI Di [2-(diethylthionophosphonothio) ethyl] terphthalate To a stirred solution of 0.1 mole of ammonium diethyldithiophosphate in 100 ml. of methyl ethyl ketone was added, over 0.5 hour, 0.4 mole of di-(Z-chloroethyl) terphthalate while maintaining the solution at the reflux hours at room temperature to leave the desired product as a residue.

EXAMPLE XXII Di [2-(dimethylthionophosphonothio) ethyl] -2,5- dimethoxy terphthalate To a stirred solution of 0.1 mole of ammonium dimethyldithiophosphate in ml. of n-butanol was added,

over 0.25 hour, 0.45 mole of di-(2-bromoethyl) terphthalate while maintaining the solution at the reflux temperature. Refluxing was continued for 0.5 hour and at the end of this period precipitated ammonium bromide was removed by filtration. The filtrate was concentrated in vacuo at room temperature. The residuewas taken up in 100 ml. of benzene and the resulting solution washed twice with 25 ml. portions of water. The organic layer was separated and dried over sodium sulfate. The drying agent was removed by filtration and the dried filtrate concentrated at 0.5 mm. of mercury for twelve hours at room temperature to leave the desired product as a residue.

What is claimed is:

1. A compound of the formula active ingredient a compound of claim 1 dispersed in a semi-solid extending agent. I

5. A pesticidal composition containing as its principal active ingredient a compound of claim 1 dispersed ina liquid extending agent. 6. A method of killing mites which comprises contacting said mites with a compound of claim 1.

References Cited in the file of this'patent I UNITED STATES PATENTS 2,710,301 Morris et al. Sept. 30, 1955 2,791,574 Lanham May 7, 1957 

1. A COMPOUND OF THE FORMULA 